Gradually flatten overlapping vertices on XY-Plane
You could select all vertices along the rightmost edge of the ocean, activate proportional editing with a sufficiently large radius and scale to zero in Z-direction.
(Will try to post screenshots later, if necessary!)
In case you want to keep the ocean modifier, you might be interested in using the lattice modifier 
With the lattice vertices scaled to zero height at the right side, the ocean will gradually lose amplitude towards the right. Use the &quot;linear&quot; interpolation to get it totally flat on that side.